Non-commercial political parodies fall under the fair use provisions of U.S. Code Title 17 Sec. 107, which consider:
- the purpose and character of the use, including whether such use is of a commercial nature or is for nonprofit educational purposes;
- the nature of the copyrighted work;
- the amount and substantiality of the portion used in relation to the copyrighted work as a whole; and
- the effect of the use upon the potential market for or value of the copyrighted work.
My personal belief is that a libertarian society may recognize intellectual property in expression only to prevent unauthorized reproduction in cases of a) competition that diverts commercial benefit from the owner to the competitor, b) attributed use with unattributed defamatory modification, or c) unattributed use that misleads about who the owner is.